Spatial Distribution,Source Analysis,and Risk Assessment Of PAHs In Snow Cover In Harbin City

In recent years,with the rapid development of urban construction and industrial activities,the types and content of pollutants discharged by humans into the ecological environment are also increasing.Excessive pollutants have caused certain harm to human health and the ecological quality of the environment.Polycyclic aromatic hydrocarbons（PAHs）are a class of persistent organic pollutants that commonly exist in the environment,and widely exist in the atmosphere,precipitation,and surface and underground water bodies.In addition to some natural sources,such as the biosynthesis of terrestrial and aquatic organisms and volcanic eruptions,the vast majority of PAHs also come from the emissions of pollutants from human life and most industrial activities.Due to their"three effects"of carcinogenesis,teratogenicity,and mutagenicity,PAHs are listed as toxic and harmful pollutants that are prioritized for control by countries around the world.Taking Harbin,the capital city of Northeast China,as the research area,this article collected samples of urban snow cover in the winter of 2020,analyzed 16 types of PAHs in the samples,explored the spatial distribution characteristics,source analysis,and risk assessment of PAHs in the winter of 2020 in Harbin.The main conclusions are as follows:（1）In the snow cover samples collected in this paper in Harbin,16 dominant PAHs were detected,with a total mass concentration range of 1705 ng·L^-1-7243 ng·L^-1,a mean PAHs value of 3014.8 ng·L^-1,a median sample value of 2683.2 ng·L-1,a standard deviation of 1369.612 ng·L^-1,and a coefficient of variation of 45.43%.The highest proportion of 3-ring PAHs was detected,accounting for about 40.95%,while the lowest proportion of 6-ring PAHs was 6.11%.The monomer ratio of Nap was the highest,reaching 14.71%.（2）The spatial concentration of PAHs with different ring numbers varies significantly.High ring PAHs account for a large proportion in areas with high traffic flow,while low ring PAHs account for a significant proportion in residential areas.However,there is also high ring PAHs pollution.According to actual situation analysis,it can be seen that there are coal burning and wood heating conditions in residential areas,especially in suburban residential areas,in winter,and the presence of tractors with large exhaust gas pollution leads to the existence of mixed pollution sources.（3）The source of PAHs in the snow cover in Harbin was analyzed by using the isomer ratio method and the positive definite matrix factorization model（PMF）method.The results obtained from the analysis were the same,both of which proved that the main sources of PAHs in the snow cover in Harbin were exhaust emissions and the combustion of grass,wood,and coal,with gasoline as the main source of exhaust emissions.Spatial interpolation was performed on the data results.Analysis of the spatial interpolation results showed that the pollution contribution of petroleum combustion was high among the polycyclic aromatic hydrocarbon sources in the S1,S12,S19 sampling points,and the surrounding areas of S4,S8,and S9 sampling points,while the contribution of grass,wood,and coal was high in the remaining areas.The actual situation of areas where oil combustion is the main source of pollution contribution includes a large number of important highway loops and highway passenger stations.（4）Using the Ba P based toxicity equivalent factor for ecological risk assessment,it was found that only 2 of the 7 sampling points in the traffic function zone met national standards;Among the 5 sampling points in the functional area of the industrial zone,2comply with national standards;Among the 6 sampling points in residential functional areas,5 meet national standards;Four of the five green space functional areas meet national standards.This result indicates that there are some areas in Harbin with extremely serious ecological risks,and the environmental pollution caused by traffic exhaust emissions and industrial emissions needs urgent attention.Through spatial analysis of TEQ_{Ba P} values and comparison between Kriging method and inverse distance weighting method,it is found that the ecological risk of polycyclic aromatic hydrocarbons in Harbin in winter is relatively serious in space.Based on the lifelong carcinogenic risk assessment model（ILCR）,the carcinogenic risk was evaluated,and spatial interpolation analysis was performed on the data.It was found that the vast majority of the sampling areas had negligible carcinogenic risks to humans and potential carcinogenic risks to humans,but there were still three areas with unacceptable carcinogenic risks,which were consistent with the three areas with the most severe polycyclic aromatic hydrocarbon pollution,This indicates that polycyclic aromatic hydrocarbons（PAHs）pollution can have a relatively serious impact on the human body,requiring early attention and treatment.